Telephone-exchange system



O. H. KOPP TELEPHONE EXCHANGE SYSTEM Jan.1`1,1927. l 1,613,613

mmm

Filed April 1 192,5 y Qsheets-Sheet 2 y y/Wy 1 A1,613 Jan.11,19z1. o. H. KOPP ,613

TELEPHdNE EXCHANGE SYSTEM Filed April 1, 1925 9 sheets-sheet s Jan. 11,1921. 1,613,613

- O. H. KOPP TELEPHONE EXCHANGE SYSTEM 1,613,613 O. H. KOPP TELEPHONE EXCHANGE SYSTEM Filed Ap l.1 29?.

Jan. 11 1927.

- /m/eU/ar-: @mmf/x KW Jan. 411, 1927.v 1,613,613

O. H. KOPP 4 TELEPHONE EXCHANGE SYSTEM Filed April 1925 9 Shee t Jan. l1 ,1927.

n 1,613,613 o. H. KOPP TELEPHONE EXCHANGE SYSTEMV Filed April 1 192s @f A1134l l Jan. ll 1927. 1,613,613

o. H. KOPP I TELEPHONE EXCHANG SYSTEM y Filed April 1 1925 9 sheets-sheet' a Jam u, 19m. mman O. H. KOPP TELEPHONE EXCHANGE SYSTEM Filed April 1 l925`v 9 Sheets-Sheet aaa-Af Patented Jan. 11, 1927.

"unirse s'ra'rss OTTMAB. H. KOPP,` OF BROOKLYN, NEW YORK,

ASSIGNR, BY MESNIL@ ASSGIHVENTS, TO

TELEPHONE-EXCHANGE SYSTEM.

Appiicauon fue-.d Api-n 1, .19125. sei-iai No. 19,759.

The present invention relates to a telephone system in which connections are established by means of automatic switches.

In the case of power driven apparatus, register senders are employed to control the extension of connections. Heretofore it has been customary if the apparatus failed to function correctly and did not vcomplete selec tions within a specified time, that a signal "was transmitted to an operator who then Arel-eased the connection. Also, if the subscriber abandoned the call before the completion of the connection, the appaiatus operated to inform the operator, l'who would then release the sender and apparatus associated with the subscribei"s line.

It is an object of the present invention to provide means for automatically releasing the register sender if a call is not completed within a reasonable time.

A feature of the invention lies in means for opening' the connection between the distri ct selector and the register sender in order to disnins the sender.

Another feature of the invention lies in a timing switch for insuring` a predetermined interval before causing the dismissal of the sender.

Another feature of the invention lies in means for providingl a longer time interval 'lxetore the dismissal of the sender in the case of outgoing calls to mechanical otiices.

An additional feature of the invention lies in means for preventing,` the wipe out of calls to manual otces and the signaling,v of a monitoring' operator during any desired period ot' the day.

A. further feature of the invention lies in the restarting of the timing switch at the beginning` of the succesiv-e stages of the eX-f,

' tor operator ofthe stage of the establishment ot' a connection which was unduly delayed.

This' larrangement has been disclosed in connection with a sender suitable foruse in tandem otiices such as disclosed in Pat-ent No. 1,501,871 to F. A. Stearn, issued July 15, 192i. i

This disclosure similar to that of applicationSerial No. 19,5841, tiled March 8l, 1925, in the name of L. H. Johnson and T. H.

Roberts and similar reference numerals have, therefore', been applied to parts correspondto those in the above identified application. Certain portions of the disclosure not essential to an understanding of the present invention have been indicated by dotted rectangles, as will be clear from 'the following description. yFor a full description of the complete circuit reference may be had to such application.

Referring' now tothe drawings, Fig. 1 shows in diagrammatic formasubscribers line with selectors for extending-'said lines and a 'sender for controlling such selectors.

Fig. 2 shows a strict selector at a tandem otice.

Fig'. shows an outgoing` selector atthc tandem oflice, the incomingl and final selector at a third office, and call indicator apparatus at still another oitice.

Fig. l shows a link circuit for associating the sender andthe districtselector of Fig. 2.

' Fig'. 5 shows a timing` switch and means for controlling` the wiping out of an uncompleted call. y

Fig. 6 shows the means for receiving' codc impulses from the distant oftice andthe transfer relays for directing the registration of said impulses. Y i

Fig. 7 shows the counting relays and sequence switch for controlling selections.

rat-us for controlling the selection and setting of a translator. i

Fig. 9 shows the class switch and the relay call indicator impulse generating switch.

Fig'. 10 shows the arrangement of Figs. 1 to 9, inclusive, in order to make a complete disclosure of the invention.

Call to full mechanical oyce. Assume that the subscriber at substation 100, located at office X, desires to talk to al to tandemdistrict selector 20() at the tandem F ig. Sshows a sequence switch and appa- V Aabove mentioned application of L.

oliic-e Y. For a description of the registration of the wanted number on the sender and the action of said sender in controlling the extension to an outgoing trunk reference may be made to U. S. Patent 1,395,977 to F. A. Stearn, et al., granted November 1, 1921, and for a description of the method of sending code pulses reference may be made to Patent 1,404,084, to A. Lundell et al., issued August 7 ,v 1923.

Nhen oliice selector 103 connects with trunk 249-1250, a relay (not shown) at sender 104 will be bridged across conductors 249 and 250, completing a circuit for relay 201 which may be traced from battery at the outer left back contact of relay 234, right winding of relay 201, lower left` contact of cam 203, upper bach contact ot relay 202, over trunk conductor 249, through office selector 103, and district selector 102, through the above mentioned relay in the sender 104, back through district selector' 102 and oliice selector 103, trunk conductor 250, inner lower back contact of relay 202, lower right Contact ot cam 204, lett winding ot' relay 201,

inner -right back contact oi relay 234 to ground. The operation ot relay 201 closes a circuit from battery through the winding of relay 205, lower right contact o't'cam 206, outer left back contact oi relay 207, lower contacts ot' cam 208, iront contact of relay 201 to ground. When relay 205 operates it closes a circuit from lground at its inner lett front contact over the upper right and lower lett contacts ot cam 209, conductor 405 and thence through apparatus (not shown) to relay 400 associated with allotter switch 410. The allotter switch shown in detail in the H. Johnson, et al., is represented by the rectangle at the lower lett corner of Fig. 4. Relay 400 closes a circuit (not shown) for operating rela-y 408. Relay 408 operates and closes a circuit from batteryV through the winding ofrelay 503, lett back contact of relay 502, contact of jack 50,1, conductor 411, contact of relay 408 to ground. Relay 503 in operating locks over its inner right contact, right back contact of relay 502, conductor 504 to ground at the contact ot relay 400. Relay V503 in operating also closes a circuit from battery, through the winding of relay 505, inne-r lei't contact ot' relay 503 to ground. The circuits closed by the operation of relay 505 will be discussed later.

Relay 503 also closes a circuit 'from battery through the winding of start magnet 510, back contact ot stop'magnet 511, outer left contact ot relay 503 to ground. The power driven switch 500 is rotated under the control ot magnet 510 until brush 512 engages the terminal connected to the district selector 200, which terminal is connected with ground, thus closing a circuit from battery, through the winding of relay 508, and from battery through the winding of stop magnet 511 and back contact of relay'518, in parallel, over the 'outer rightcont'act 'of relay 503, brush 512, and the terminal corresponding to selector 200, conductor 509, lower contacts 01E cam 212, outer lefty front contact of relay 205, right contact of cani 213 to ground.

It will be noted that in the case of a district selectorvwhich has not been selected for use relay 205 will not be operated and the path from ground will not be extended to the terminals of finder switches. Relay 508 and magnet 511voperate in the above traced circuit, magnet 511 serving to open the circuit ofV magnet 510, bringing the switch 500 to rest on :the terminals leading to selector 200. Relay 508 closes akci'rcuit from battery through the wind-ing of relay 518, outer right front contact of relay 508 to ground.

Relay 518 operates and closes a locking circuit for itself over its inner right contact, lei't windingvof relay 519, brush 513 to conductor 528, from whence the circuit is extended to ground as will be subsequently described. Relay 518 also closes an obvious circuit for relay 502, closes a holding circuit tor magnet 511 at its inner left alternate contact, and closes a new holding circuit :tor relay 503 which extends over the inner right Contact of relay 503, inner right front contact ot relay 508, outer left contact of relay 518, outer lett front Vcontact of relay 503 to ground.

The operation of relay 502 opens the first traced locking circuit for relay 503, closes a holding circuit for relay 505 at its middle right contact, and closes a circuit from battery through the left winding of relay 207, upper left and lower right contacts of cam 214, Vconductor 529, brush 514 and its corresponding terminal, leit front contact of relay 502, left contact of relay 508 to ground. Relay 207 operates and locks over its outer lett iront contact, lower contacts of cani 208, to ground at the front contact of relay 201. The operation of relay 207 opens the circuit of relay 205'which relay releases, opening the circuit of relay 400. Relay V207 also connects ground from the front contact ot relay 201, lower contacts oi cam 208, right front contact of relay 207, lowercontacts of cam 215, non-inductive resistance 216, to conductor 528, completing the locking circuit of relay 518, which waspreviously traced to conductor 528. Relay 519 being marginal does not operate through resistance 216.

Relay 207 also closes a circuit Jfrom battery through the winding of sequence switch magnet-210, upper lett contact ot cam 217, inner left trent contact ot relay 207, upper left and lower right contacts of cam 218, back contact o't' relay 205, right contact ot cani. 213 to ground, advancing sequence switch 210 to position 3.

ln position 2 ot sequence switch210 the locking circuit of relay 518 is extended over the upper right contact ot cain 219 to ground, Where it is maintained until sequence switch 210 leaves position 13. The release ot' relay 205 as previously described also removes ground 'troni conductor 509, thus opening the circuit o't relay 508.

The release of relay 508 opens the locking circuit ot relay 503 and that relay alfio releases. When sequence switch 210 reaches position 3, the circuit. oit relay 201 is ef;- tnded troni battery, outer lett baci-i contact ot relay 23d, right winding ot' relay 201, right contacts of cani 218, lett baci; contact of relay 205, lower right and upper left contacts ot cani 203, conductor 249, and thence as previousil y traced to conductor 250, lett contacts of cani 20a, right back contact ot relay 205, lett Winding of relay 201, right. back contact ot relay 23d to ground, so that relay 201 is maintained energized.

In the ineantinie the opta-ation ot relay 505 as previously described closes a circuit Vroin battery through the winding of relay 530, right back contact ot relay 531, outer right front contact of relay 505 to ground.

. Relay 530 operates and loclrs over its right front contact, back contact ot stop niagnet 521, outer right contact ot relay 505 to ground. lt also closes a circuit troni battery through the Winding ot' allotter uuuI iet 410, lett contact ot cani T1513, conductor 532, contact ot jack 501, left contact ol relay 505 to ground, advancing allotter 410 to positionV 2 in which position it is ready to allot another link circuit for use in connection with a subsequent call,

The operation ot relay 530 closes a circuit- 'tron'i battery through the Winding of relay 531, inner lett tront Contact of relay 530 to ground at the outer right contact of relay 505. .Relay 531 closes a circuit from batteryV through the start magnet 520` which conV trols the operation ot' switch 550, outer right front contact o1 relay 531, right iront contacter rel y 530, back contact otinagnet 521, outer right iront contact of relay 505 to ground. lt also opens the energizing tated under the control of nia-guet 520 until it engage-s an idle sender which isV characterized by battery through a resistance connected to conductor (501. lVhen an, idle render is reached, a circuit `is closed from battery, inner back contact oli' relay 701, resistance ri500, conductor 601, terminal .fiervedvby brush` corre-Spending to the idle sender, inner rieht contact ofrelay 505,. Vboth windinos g ot relay 533, Winding oi' relay 53e, outer right contact of 'relay 505' to ground.'

Relay "93 operates and short circuits i ts high rewtance Winding pernxitting iur ginal relay 53% to operate. rl`he operation ot relay 531i closes a circuit troni battery tnrough stop magnet contact of circuit et relay Switch isthen roings relay 201.

ing circuit of' relay 530 and the energizing circuit for magnet 520. Relay 530 and niagnet 520 release. VRelay 530 on` releasing.;Y

4closes a holding circuit for magnet 521 over the inner lett lront contact of relay 531, right back contact ot relay 5,30, outer right contact ol' relay 505 to ground; This circuit is in shunt of the windings ot relays 533, and 53% so that vthese relays also release. With relays 530 and 503 released and relays and 531 operated a circuit is closed troni battery through the Winding olE relay 535, outer right iront contact ot relay 502, outer lett back contact ot relay y530, outer lett contact ot relay531, right back contact ot relay 508 to ground. Relay 535 in operating extends the fundamental tip and ring conductors and certain control conductors Vtroni the district selector to the sender. lt also closes a circuit trom ground through resistance 530, brush 523 and its corresponding bank terminal, Yconductor- 002, lett u'iudingot relay 603, outer lett back contact of relay 701,l Winding oi' relay T02 to battery. Relay T02 operates, but relay 303 being marginal does-not. Relay 7 02 lock-ff. to its energizing circuit independent ci the contact ot relay 701.

telay 702 also closes an obvious energizing circuit for relay 701 which in operating re-` inoyes battery Vtroni conductor 001 to niark the tender busy to other link circuits. The operation otrelay 535 also closes a circuit troni battery, through the nf'inding otrelay 205, lower contacts ot ca1n21il, conductor 520, brugh 514C and `the terininal served thereby, right Winding of relay 519,inner lett contact of relay 535, brush 52a and its corresponding tern'iinal, right Winding of relay 003, lett bach contact of relay 604C, right bach contact ot relay 703, inner left 'trent contact oi' relay `702 to ground. Relays 519 and 003 being dil'lerential the. coinpletion of this circuit does not cause the operation of either relay. elay 205 operates and'connects the trunk conductors 249 and 250 through to the pulsing relays of the sender, disconnecting` them troni the l,Wind- This relay releases and releasesrelay 207.

.Relay 702 in operating also closes a circuit 'troin battery, through the Winding of relay (305,.No. 1 terminal and brush 61eL of :tuning switch 600,'left baclrcontact of rclay` 606, conductor 607, upper left cont-act `oit cam 1000, upper left contact of relay sov i nl

relay 707, inner lett back contactV olf relay 7 04, lett contacts of cani 900, conductor 013, brush 525, inne" right contact of relay 535, brush 515, conductor 537, lower contacts of earn 220, outer right front contact of relay 205, lett contacts otcain 204, conductor 250 `and thence through the ottice and district selectors to the sender 104.

The coinpletion of this circuit, due to the operation of relay 205, initiates certain operations at the sender 104 which result in the transmission ot code impulses to correspond to the nuinber Aot the wanted line. For a description of these operations relerence inay bein-ade to the above iuentioi'ied Patent No. 1,464,084 to A. E. Lundell, et al., issued August 7, 1923. y

The code ii'npulses consist ot light and heavy negative pulses and positive pulses. The light negative pulses cause the operation ot relay 700, the heavy negative pulses the operation otl relays 706 and 705, and the positive pulses the operation ot relay 707. The operations of relay 700 serve to control a cycle ot' operations ot relays 708 and 709, which in turn control the operation ot the pairs ot transfer relays 710, 711, etc. A

pair of transfer relays is operated in response to the code pulses representing each digit. The operation of relay 705 or relay 707 causes the operation of certain relays in the registers indicated by rectangle 800, according to which set of transfer relays have last been operated. For the operation of the transfer relays and ot the register relays of rectangle 800 reference may be inade to the above inentioned application of L. H. Johnson, et al. Then relayv716 operates, after the reception ot the stati-ons pulses, as de-' scribed in the above' identified application,

a circuit is closed troni battery, through the winding vof sequence switch ina'gnet 1010, lower fright contact of cani 1004, outer left back contact of relay 1005, outer left front contact of relay 716 to ground, ad-

vancing switch 1010 to position 2. Then the last code Viiiipulse has been received and relay 704 operates, a circuit is closed trein battery, through the winding ot relay 703, outer right front contact of relay 704 to ground. Relay 703 `operates and locks over its inner right front contact to ground at the inner lett front contact ot relay 702.

The ope ation of relay 703 opens the fundainental circuit, preventing the reception of any further pulses. Y

The operati-on of relay 703 opens the circuit ot relay 205 which relay releases and again er1-tends the trunk conductors 249 and 250 to the windings of relay 201. District selector 102 now coinpletes a loop over the trunk coiiductorsl whereupon relay 201 is again operated. The operation o'l' relay 201 closes a circuit troni battery through the winning of relay 222, lett contact ot' cani 200, outer lett baci; contact of relay 207, lowercontacts ot cani 208, front contact of relay 201 to ground. elay operates and locks over its lett yfront contact and the lower left contact ofcani 223 to ground at `the upper lett Contact of cain 223 through position 31/2 of sequence switch 210 and then in positions 3% to 7 to ground over the lower right contact of cain 223 and the l'ront contact et' relay 201. The operation 'ot relay 222 closes a circuit from battery through the winding ot' sequence switch magnet 210, lett contact ot cani 224, inner left back contact of relay 207, right front contact of i'elay to ground advancing the sequence switch to position 4.

As soon as switch 1010 reaches position 1% ground is connected over the lower left contact ot' cani 1006 to conductor 330, which is extended by .nieans of registers 800 to control the setting ot secondary registers, which are indicated by rectangle 1100. Then these secondary registers are positioned, a circuit is closed over the lower le'lt contact ot' cam 1004 to advance sequence switch 1010 to position 4. In accordance with the position taken by secondary registers 1100, one of the relays 1007, 1011, 1012 or 1013 isV operated to cause a translator finder 'to select a translator and connect it with the sender. The translator linders and translators are indicated diagrainn'iatica-lly by `the lrectangle 1050. The translator is positioned by means ot revertive impulses, in a manner siinilar to the selection of a sub* scribers line by a final selector. For' a coinplete description ot the selection'of a translator and the positioning of the sanie, reference niay be inade to the Aabove identilied application of L. H. Johnson, et al. Sequence switch 1010 is advanced from position to position as the translator is set and when the translator eonies to rest on the terminals selected by the positioning of registers 1100, switch 1010 will be in position 11. As soon as switch 1010 reaches position 10, a circuit is closed for relay 1027 over the lower lett contact ot cain 1024, which connects the translator to the tertiary registers represented by rectangle 1300. The tertiary registers`1300 aie then set under the control of the translator. Then they have been coinpletely set, sequence switch 1010 is advanced to position 12. As soon as switch 1010 leaves position 11, the translator finder and the translator are disconnected from the sender.

lVhen the registers 1300 have been positioned circuits are completed for positioning class switch 1200, in accordance with the class ot call to be extended. Switch 1200 sets up the proper conditions for completing the call and also selects the proper stepping relay and testing resistance to be included in the fundamental circuit according to the resistance of the trunk over which such fundamental circuit extends. Rectangles 1300 and 1300A represent the same setl of regisi ters, but have been separated 'for convenience of drawing.

Relay 1202 is energized in parallel with sequence switch 1200 and ieleaseswvhen the switch comes to rest toclose a circuittrom ground over its back contact, conductor 1032, upper left contact of cam 1031, conductor 727, outer right front contact of relay 703, conductor 728, lower left contact of camY 920, winding of sequence switch magnet 910 to battery, advancing this sequence switch to position 2.

lith sequence switch 910 in position 2` a circuit is completed from battery through the winding of sequence switch magnet 1010, lower right contact of cam 1025, lower left contact of cam 921 to ground, advancing sequence switch 1010 to position 13.

`With sequence switch 1010 in position 13 and sequence switch 910 in position 2 the fundamental circuit is completed from battery through the lett winding of relay 207, lett contacts ot cam 221, conductor 538, brush 510, middle right contact of relay 535, brush 520, conductor G19, upper left contact ot' cam 1019, conductor 1020, lower contact ot cam 901, back contact of relay 902, winding of relay 903, winding ot relay 904, lower lett contact ot' cam 1201, (assuming switch 1200 is now in position 8 to correspond to a call to a mechanical oiiice), contact of cam 1021, lower Contact of cam 906, resistance 907 to ground. Relays 904 and 207 operate in this circuit.

Relay 207 locks over its outer left front cont-act, upper left contact of cam 212, upper left contact o1 cam 221, to conductor 538 and thence over the fundamental circuit as traced to ground. The operation of relay 207 closes a circuit from battery through the winding of sequence switch magnet 210, upper left contact of cani 217 inner left front contact of relay 207, front contact of relay 222 to ground. Sequence switch 210 advances in this circuit to position 5. In position 5 the energizing circuit of relay 207 is opened but the locking circuit is maintained closed. A circuit is completed for updrive magnet 225 over the upper right and lower lett contacts of cani 226, inner left front Contact of relay 207,` right front contact of relay 222 to ground. As the brush rod moves upward an intermittent circuit is completed from battery, lett winding of relay 207 outer left iront contact of relay 207, upper lett contact ot' cam 212, upper left contact ot cam 221, lower left and upper right contacts ot cani 227, commutator strip 228, brush 229, lower left contactot cain 219 to ground.

Relay 904 closes a circuit from battery at the inner left contact of relay 701, conductor 022, through one of the counting relays overone of the conductors 913, 919, 922, 908 or 934, through contacts of the registers shown at 1300A over the upper right and lower left contacts of cam 950, upper right contact of cam 1000, lower lett contact of cam 1001, conductor 1023, upper right and lower left contacts of cam 909, front contact ot relay 904 lower lett contact of cam 911 to ground.

The counting relays operate in the usual manner, locking through Vthe winding ot the corresponding prime counting relay. When the above traced intermittent circuit is close-d, relay 904 is shunted and the prime counting relay operates'. Each time tha the intermittent circuit is completed a pair ot counting relays lock up to extend the circuit to the next pair of counting relays; `When this circuit has been completed a sutticient number of times, relays 915 and 902 are operated in the locking circuit of the No. 0 counting relay, which may be traced from battery at the left Jfront contact of relay 701, conductor 622, winding ot the No. 0 counting relay, windings of relays 902 and 915 in parallel, tront contact of the No. 0 counting relay, upper lett contact of cam 925 to ground. Relay 902 serves to open the fundamental circuit permitting the release 'of relay 207. Relay 915 closes a circuit t'rom battery through the winding ot sequence switch magnet 910, upper right contact of cam 924, inner` right back ccntact of relay 918, iront contact of relay 915 to ground, advancingthe sequence switch 910 to position 4. In passing from position 2 to position 4 sequence switch 910 opens the locking circuit of the counting relays i and they release.

The release of relay 207 opens the circuit of updrive magnet 225, bringing the selector 200 to rest. Relay 207 in releasing closes a circuit from battery through the winding` of sequence switch magnet 210, lower left contact oit' cam 224, inner lett back contact of relay 207, contact ot' relay to ground advancing the. sequence switch toposition (i.

TWhen sequence switch 210 is in position 6 and sequence switch 910 in position 4 the fundamental circuit is again established. Relay 207 operates and locks as "above and advances sequence switch 210 to position 7 in which position the energizing circuit of,

lll)

rae

CII

relay 207 is opened but the locking circuit is maintained. As soon as sequence. switch 210 reaches position 6 a circuit is completed through trip magnet 230, lower right contact if cam 219 to ground. In position 7 the eircuit of updrive magnet 225 is again estab. lished 4over the upper right and lower left contacts of cam 226, inner lett t'ront cont-act of rel-ay 207 to ground at the front contact of relay 222. Relay 90eL in operating closes the usual counting relay circuit, including the registers ot 1300A.

AnY intermittent circuit is completed through the lett winding of relay 207, outer lett front contact ot relay 207, upper contacts ot cam 212, commutator strip 231, brush 232, lower le't't contact of cam 219 to ground. As before, this circuit is completed each time that brush 232 encounters a conducting segment ot strip 231. The completion ot this circuit causes the operation and locking of a pair of countingl relays in the usual manner. Then it has been completed a suliicient number ot times relays 902 and 915 operate in the locking circuit of the No. 0 counting relay, which is the same as previously traced. vRelay 902 opens the fundamental circuit to release relay 207 and relay 915 operates to advance sequence switch 910 to position 5.

The release oi relay 207 opens the circuit ot updrive magnet 225, bringing the switch to rest with the brushes upon the first terminals ot the desired group of outgoing trunks. At its inner left back contact relay 207 closes a circuit Jroi advancing sequence switch 210 to position 8. lilith sequence switch 210 in position 6, relay 207 is operated in a local circuit extending from battery, through its right winding, lower contacts of cam 233, inner left back contact ot' relay 234-, right front contact of relay 222 to ground. Relay 207 operates and locls in a circuit from battery, through its left winding and outer left and right front coin tacts, lower lett and upper right contacts ot cam 215, to sleeve brush provided that the iirst` trunk ot the group is busy.

The operation ot' relay 207 also closes a circuit trom battery through the winding' of sequence switch magnet 210. upper lett Contact of cam 217, inner lett front contact ot relay 207, to groundat the right trant contact. of relay 222, advancing sequence switch 210 to position 9. It the tiret trunk ot the group is idle relay 207 releases inn mediately that the sequence switch leaves position 81@ Should the lirst trunk be busy, however, relay 207 is held opera ted to close a circuit through updrive magnet 225 extending over the upper right and lower left contacts of cam 226, inner lettfront contact oit' relay 207, front contact ot relay 222 to ground. Switch 200 will be advanced under the control ot' the updrive magnet in Search ot an idle trunk. Relay 207 is maintained energized between terminals by means ot a. circuit through its right winding` lower left and upper right contacts ot cam 233, centering commutator strip 286, brush 287, lett contacts ot' cam 226, inner lett trent contact ot relay 207 to ground at the front contact ot relay 222.

`When brush 235 encounters an idle outgoing trunk, relay 207 is released as soon as its brushes are properly centered and the holding' circuit through the centering strip 286 is broken. As soon as relay 207 releases the circuit ot updrive magnet 225 is opened, and a circuit is completed from battery through the winding of sequence switch magnet 210, lower left contact ot cam 224, inner lett back contact of relay 207 to ground at the Yfront contact ot' relay 222 to advance the sequence switch to position l0. As soon as relay 207 releases, it connects ground from the upper right Contact ot' cam 206, over its outer left back contact, right contacts ot cam 208, to the sleeve brush 235 to niark the terminal busy. When sequence switch 210 arrives in position 10 ground is connected to brush 235 `over the upper contacts ot cam 208, independent oi relay 207.

ln position 10 ot sequence switch 210, direct ground trom relay 222 over the lett contacts ot cam 218 is connected in shunt ot the ground through resistance 216 to conductor 52S, and thence over brush 513, through the le't't winding of relay 519, front contact and winding of relay 518 to battery. Relay 519 now receives suliicient current to cause it to operate It connects direct ground from its liront Contact over brush 523, conductor 602, left winding ot relay 603 to the front Contact and winding of relay 702. Relay 603 now receives sufficient current to cause it. to operate and it closes a circuit from battery through the winding oi sequence switch magnet 910, lower lett contact ot' cam 921i, trout Contact of relay 603 to gro-und, advancing sequence switch 910 to position 6.

lilith sequence switch 910 .in position 6 a circuit is closed from battery through the lett winding ot' relay 207, upper lett and lower right contacts ol cani 214, conductor 529, brush 51a, right winding of relay 519, inner lett Contact oi? relay 535, brush 5%, right winding otrelay S, back contact of relay 604, back contact o' relay 623, lower lett Contact ot cam 925 to ground. Relay 207 operates in this circuit and closes a cir cuit from battery through magnet 210, upper lett contact ot cani 217, inner let't trout contact ot' relay 207, front contact oit' relay to ground advancing the sequence switch to position l1. In this vposition subfeoluent selections talre place and the fundamental circuit from the sender is connected through to the oftiee selector of lVhen sequence switch 210 leaves position 10 the direct ground is removed from conductor 528, leaving only the ground through re.- sistance. 216. Since relay 519 is differential the circuit just traced for relay20? now causes relay 519 to release. The release ot relay 519 removes direct ground from tue winding' ot relay 603 so tl at, since relay 003 is' also ditlerentially wound, the above traced circuit for relay 207 causes the release of relay 603 as well.

The fundamental circuit is now clozged for testing; the oliice selector'. A circuit is closed from battery, through the lett winding of relay 301, lower leftcontact ot cam 302, lower left contact ol' cam 303, district selector brush 236, lower contacts of cam 227, conductor 533, brush 510, middle con-V tact ot relay 535, brush 526, conductor 619,

upper lett contact ot' cam` 1019, conductor 1020, lower contact of cam 901, bach Contact of relay 902, winding,v oit relay 903, contact of cam 1205, winding of relay 926, resist? ances 1206 and 1207, lower contact ojl cam 92T, upper left and lower right contacts of cam 923, Aright baclrcontact of relay 1033, lower right Contact of cam 950, upper lett contact oli' cam 900, conductor 013, brush 525,'inner right contact ot' relay 535, brush 515, conductor v537,1ight contacts ot cam 220, district selector brush 23T, resistance 352, left contacts ot cam 353 to ground.

it' the oli-ice selector and relay 301 in that selector are in normal condition the above traced circuit is completed. and relay 926 .operates but relay 301 does not; The operation oit relay 923 closes an obvious circuit 'for relay 929, which in turn closes a circuit i'or relay 930` Relay 930'in operating locl s through its inner right front contact, upper contact ot cam .1203, lowerright contact ol cani 931 to ground. rllho operation ot relay 930 closes a circuit 'troni battery through the winding' oi magnet 910, lower le'lt contact ot' cani 932, lower right contact ot' cani 1209, lelt it'ront contact of relay 930, outer right bach contact olf relay 936 to ground, advancing` sequence switch 910 to position 3. As soon as switch 910 leaves position 6 the circuit ot relay 920 opened and that relay releases, in turn releasing relay 929. The locking circuit ol relay 930 is also opened permittinp` that relay to releaze. lllheifi switch 910 reaches position 3 the fundamental circuit entends 'from conductor 019, up per lett contact oi cam 1019, conductor 1020, lower contact ol cam 901, back contact of relay 902, winding of relay 903, winding ot relay 904e, left contact ot cam 1201, lett contact o't' cam 933, lett contact ot :ani 1031: to conductor 013 and thence as traced to ground. at cam 353. This circuit does not include resistances 1,200 and 1207 and hence relayY 301 operates therein. lit relay 301 should operate falselyin the test circuit previously traced it would advance sequence switch 310 to position 2 and blocrr the rees'- tablishment of the fundamental circuit.

The operation ot relay 301 in the fundamental circuit traced in position 8 ol sequence switch 910 closes a circuit lfioni hat tery, through the winding ot magnet 310, lower lett contact olf cani 304, outer lett :t'ront contact ot relay 301 to ground, advancing` t-he sequcncev switch to position 2. rlfhe enen-'rizing` circuit or' relay 301 is opened atthis time but a lockingl circuit extending; over its inner and middle lett front contacts, andthe upper lett contact ot' cam 302, closed while sequence. switch 310 .is still in positionA 1, `is maintained in position 2 holding` relay 301 operated. lilith sequence switch 310 in position 2 a circui is closed from battery, through the winding oi' updrive magnet 305, right contacts ot cam 303, outer left front contact ot relay 301 to ground advancing` the selector 300 inv its brush selecting opera tion.

Relay a also operates in this 'fundainental circuit and closes the usual counting relay circuit. As selector 300 moves up*- ward a circuit is intermittently closed through the lett winding of relay 301, inner and middle lett front contacts or" relay 301, upper-,left and lower right coi/itacts` ot cam 302, coinmutator strip 307` brush 308, lower lett contact of cam to ground. rllhis circuit serves to hold relay 301 operated and to shunt relay 90-/1 causingthat relay to release. This results in the operation and locking' of successive pairs ot counting re,- lays.-

1When sutlicient pairs of countingl relays have been operated, relays 902 and 915 operate in the locking kcircuit of the No, 0 counting' relay and relay 301 releases. The oper ation ot relay 915 closes a circuit 'from battery, through the winding ot sequence switch 910, upper right contact ot' cam 924, inner right back contact ot relay 913, 'lronl` contact ot relay 915 to ground, advancing' that sequence switch to 'position 10 and. releasing` the counting relays.

The release ot' ,relay 301 opens the circuit of updrivemag'net 305, lningingl .the switch to rest in position toA trip the desired set ot brushes. It also closes a. circuit from battery, winding of sequence switch magnet 310, upper left contact ot cam 304, outer lett'baclr contact of rela-y 301 to ground adv ancinp,- sequence switch 310 to position 3. As soon as the sequence switch reaches position 3 a circuit is established for trip inaguet 313 over the upper right contact ojt cani 315 to ground, .so that when switch 300 is again moved upward the desired set oiI brushes will be tripped.

With switch 910 in position 10 and switch 'fundamental circuit is described and relays 301 and 901 operate as betore. Relay 301 locks and closes the previously traced circuit for advancing sequence switch 310 to position el. In position e the locking circuit of relay 301 is maintained and the previously traced circuit 'tor updrive inagnet 305 reestablished. Relay 904 in operating closesthe usual counting relay circuit. As switch 300 inoves upward, brush 311 coinpletes an intermittent circuit through the lett winding` ot relay 301 and its inner and middle trentA contacts, upper contacts ot cani 302, conunutatoig' strip 309, brush 311, lower lett contact otl cani 353 to ground.

lVhcu thisr intermittent circuit has been 310 in position V3 the again Y established completed a sulicient nuinher ot tinies, re-V lays 915 and operate in the locking; circuit otl the No. 0 counting relay. Relay 902 as bet'ore, opens the fundamental circuit permitting the relay 301 to release as soon as brush 3.11 loaves the conducting segment of strip 309. Relay 915 cloes the uf-ual circuit to ad 'ance sequence switch 910 to'position 12.

Relay 301 releasing advances sequence switch 310 toposition 5. In position relay 301 is disconnected from the fundamental circuit and is operated in a local circuit through its right winding and lett contacts ot cani 312 to ground. Relay 301 locks over its inner front contact, lower contacts ot cana 313 to .sleeve brush 314, assuming that the first outgoing trunk is busy. The operation o't relay 301 advances the sequence switch 310 to position 6, in which position the circuit ot the updrive magnet is `again closed to advance the selector 300 in search ot an idle outgoing trunk. Relay 301 is held operated between terminals by means of a circuit through its right winding, upper contacts'o't' cani 312, centering coinnuitator strip 320, brush 308, rightl contact of cani outer trout contact ot relay 301 to ground. Then switch 300 encounters an idle outgoing trunk no ground will appear on the terminal engaged by brush 314 and `the locking circuit ot relay 301is opened.

'I he energizing circuit ot' relay 301 is opened as soon as sequence switch 310 reaches position 6 and the holdingcircuit is opened as soon as the brush set is properly centered. Relay 301 in releasing closes a circuit Ytrein battery through the winding ot sequence switch 310` upper lett contact o 't cani 304, outer back contact of relay 301 to ground, advancing sequence switch 310 to po. 'tion 7. The release ot' relay 301 also opens the circuit of updrive magnet 305 so that the brushes come to rest on the selected trunk.

As soon as relay 301 releases, it connects ground over its inner lett back contact, lower contacts of cam 313, to brush 314 to mark the selected trunk busy torother outgoing selectors. As soon as sequence switch 310 reaches position 6% ground is connected to sleeve 31a over the lett contact of cani 315, maintaining the busy condition as long as switch 300 is in use. Y

In position. 7 relay 301 is operated through. its right wind-ing, left contacts of cam 312 to ground and locks over its inner and middle Jfront contacts, left contacts ot cam 316, sleeve conductor 321, district sleeve brush 235, upper contacts of cain 208 to ground. Relay 301 also advances sequence switch 310 to position 8. Switch 310 reinains in 'position 8 and relay 301 remains locked throughout the progress ot' the call.

lVhen switch 910 reached position 11 in passing to position 12 it closed a circuit from battery through the winding of sequence switch 1010, upper right contact of cam 1017, right contact of cani 921 to ground, advancing sequence switch 1010 to position 14. lVhen switch 1010 reaches position 14; it completes an additional holding circuit for relay 207 which extends from the back contact of relay 623, over the lower Contact of cam 1031, conductor 1032 to the back con-- tact ot relay 1202. This holds relay 207 operated while switch 910 passes through the tirst. part ot its second revolution.

In position 12 or' switch 910 relay 926 is again connected across the outgoing trunk,

the circuit extending at this time from conductor 619, upper left contact of earn ,1019, conductor 1020, lower contact of cam 901, back Contact of relay 902, relay 903, contact of cain 1205, winding ot relay 926, resistances 1206 and 1207, lower contact of cani 927, upper left and lower right contacts ot cani 928, lower contact of cain 10311 to conductor 618. It may be noted. that in the positions ot sequence switch 1200 corresponding to routes ot high resist-ences, resistance 1207 is short circuited to equalize the resistance in the circuit of relay 926. It the incoming selector is in position to receive a call relay 926 operates as before, in turn operating relays 929 and 930. Relay 930 locks over its inner right front contact, upper contact ot' cani 1208. lower right contact of cam 931 to ground. Relay 930 also closes a shunt around the contacts ot cani 928, holding relay 926 operated until switch 910 leaves position 14h Relay 930 also closes a circuit for advancing sequence switch 910 to position 1 extending from battery through the winding of magnet 910, lower left contact of cani 932, lower right contact ot' cani 1209, lett front contact ot relay 930, outer right back contact ot relay 936 to ground. IVhen sequence switch 910 leaves position 18 relay 930 releases. Sequence switch 910 is th'en advanced to posit-ion 2 on its second revolution in a circuit through its winding,

lower left ycontact of cam 920, conductor 7 28, outer right front contact of relay 703, cone ductor 727, upper left contact of wcam 1031, conductor 1032, back contact of relay 1202 to ground.

With switch 910 in position 2 sequence switch 1010 is advanced to position 15, in a circuit from battery through the winding of sequence switch magnet 1010, lower contact of cam 1025, lower left contact of cam 921 to ground. When switchv1010 reaches position 15, relay 1033 is operated in a circuit through its winding, upper left contact of cam 1024 to ground. With sequence switch 910 in position 2 and switch 1010 in position 15 the fundamental circuit is established from the incoming selector at station Z over the tip brush 317 of office selector 300, lower contacts of cam 303, district selector' brush 236, lower contacts of cam 227, conductor 538, brush 516, niiddle right contact of relay 535, brush 526, conductor `619 upper left contact of'cam 1019, lower contact of cam 901, back contact of relay 902, windingof relay 903, winding of relay 904, lowerleft contact of cam 1201, right contact of cam 933, resistance 937,"upper right contact of cam 1034, conductor 618, brush 525, inner contact of relay `535, brush 515, conductor 537, right contacts of cam 220, district selector brush 237, upper contacts of cam 313, brush 319 of office selector 300 to the incoming selector.

The stepping relay 904 functions in the same maner as for district selections. When sufficient pulses are received from the incoming selector, relays 902 and 915 operate as usual, advancing the incoming selector sequence switch and advancing sequence switch 910 to position 4. Y

1n position 4 the fundamental circuit is again established for incoming group selection. llllhen suilicient pulses have been ren ceived relays 902 and 915 operate advancing the incoming selector and advancing sequence switch 910 to position 5. The incoming selec-tor proceeds to hunt for an idle iinal selector in t-he well known manner. lWhen such a nal selector has been found the incoming selector advances and extends4 the fundamental circuit to the iinal selector. Sequence switch910 is advanced from position 5 over a circuit through its winding and the lower left contact of cam 924, to `,rround on the inner left contactof relay 1033.

lllith sequence switch 910 in position 6 the fundamental circuit is again established from the iinal selector for inal brush selection. `When sufficient impulses have been received relays 902 and 915 operate to advance the lin-al selector sequence switch and to advance sequence switch 910 to position 8.

1n position S the fundamental circuit is again established, this time for final group selection.` When sucient pulses have been received, relays902 and 915 operate. `As before, relay 902 causes the advance of the final selector sequence switch and relay 915 causes the advance of sequence switch 910 to positionlO. y

Final units selection. takes place when sequence switch 910 is in position 10. l/Vhen sufficient pulses have been received vrelays 902 and 915 operate as before and advance the final selector sequence switch and sequence switch 910 to position 12. The final selector proceeds totest the called line and, assuming it to be idle, advances the incoming selector to aposition in which battery is connected to the ring conductorand ground to the tip conductor thus reversing the direction of current flow over the fundamental` circuit which in yposition 12 of switch 910.V

entends from conductor 619 over the upper left contact of cam 1019, conductor 1020, lower contact of cam 901, back contact of relay 902, winding of relay 903, winding of `relay 904,'left Contact of cam 1201, right contact of cam 933, resistance 937, upper right contact of cam 1034 to conductor` 618. The current at this time is in the direction to cause relay 903 to operato. At its front contactl relay 903closes a circuit in parallel through the windings of relays 940 and 918.

l Relays 918 and 940 operate. relay 940 closing a locking circuit for the two relays over its front contact, upper left Contact of cam 911 to ground. i 4 i Relay 904 also operates. l/Vithrelays 918 and 904 both operated a circuitis closed from battery through the winding of the No. 0 counting relay, lower contact of cam 941, middle left contact of relay 918, upper contacts of cam 909, front contact of relay 904, left contact of cam 911 to ground. The No. 0 counting relay operates andloclrs as usual. The closure of the fundamental circuit as above traced causes the incoming selector sequence switch to advance, opening the fundamental circuit, releasing relays903 and 904 and permitting relays 902 and 915 to operate'. y V

vRelay 915 closes a circuit from battery throughthe winding of magnet 910, lower right contact of cam 924, inner right Contact ofrelay 936, right front contact of relay 918, front contact of relay 915 to ground, advanc-` ing the sequence switch to position 13, from which position it is advanced to position 15 by means of a circuit through its winding, upper right contact of cam 932, upper contact of cam 1036, .inner left contact of relay 918 to ground. Sequence switch 910 .is then` advanced to position 16 in a circuit through its winding, upper leftI contact of cam 920, back contactof relay 603 to` ground.

lfihen switch 910 reaches position 16 a `circuit 'is completed Vfrom batt-ery, through the windingof relay 604, lower contact of s, if.

cani 1037, lower right contact otl cam 911 to ground. The operation ot relay 604 opens the circuit through the right windings ot relays 603 and 519 and the left winding of relay 207. Relay 207 releases, closing a circuit from battery through the winding of magnet 210, left contact of cam 224, inner left back contact of relay 207, front contact ot relay 222 to ground, advancing sequence switch 210 to position 12. XVith switch 210 in position 12, direct ground is connect-ed from the front contact ot' relay 222 over the lett contacts ot cani 218 to the lett winding of relay 519, causing that relay to operate. Relay 519 in operating connects direct ground to the lett winding ot relay 603 caus ing it to operate. Vith sequence switch 210 in position 12, relay 207 reoperates in a circuitrom battery through its lett winding, lower contacts of cam 221, lower lett contact of cam 219 to ground. The operation of relay 207 closes the usual circuit for advancing sequence switch 210 to position 13 in which position relay 207 releases. Sequence switch 210 is advanced to'position 14 in a circuit trom battery, winding of magnet 210, upper right contact of cam 217, lower right contact of cam 224e, inner lett back contact of relay 207 to ground at the front contact ot' relay 222, and to position 15 in a similar circuit over the lower right contact of cam 217 and upper right contact of cam 224'.

When' switch 210 leaves position 13 ground is removed from conductor 528, opening the circuit through the left winding ot' relay 519, initiating the disconnection of the sender which will be described later.

Then the called subscriber answers, battery and ground are connected to the talking conductors at the distant otiice operating relay 238 in a circuit extending over the tip conductor through the upper winding of relay 238, resistance 239, lower contacts ot' cam 2li-0, lower winding ot' relay 238, and thence over the ring conductor. Relay 238 operates and closes a circuit from battery, through the lett winding of relay 207, upper contacts ot' cani 214, t'ront contactot' relay 238 to ground. T he operation of relay 207 advances sequence switch 210 to position 16. Relay 207 releases as switch 210 passes from position 15 to position 16, but reoperates in the latter position` through its right winding, lower contacts of cam 233, inner lett back contact ot relay 2311, to ground at the front'contact ot relay 222. The reoperation of relay 207 advances switch 210 to position 17.

Then switch 210 reaches position 155/4 a circuit is closed from battery, winding of relay 202, upper lett and lower right contacts ot' cam 233, inner left back contact of relay 2341, front contact of relay 222 to ground. Relay 202 in opera-ting extends the talking conductors through tandem office Y to office Z. rEhe operation of relay 202 also disconnects relay 201 from the talking conductors and closes alocal circuit tor holding that relay operated from battery, outer lett back Contact ot relay 234, right winding of relay 201, lower left contact of cam 203, lower front contact ot' relay 202, front contact of relay 238 to ground. The bridged resistance 239 is maintained across the talking conductors until the sequence switch leaves position 16. Conversation takes place in position 17 of the district selector sequence switch.

When ground is removed from conductor as previously mentioned, relay 519 releases opening the circuit through the lett winding of relay 603, and the` winding ot' relay 702. Relays 603 and 702 release. lVith relay 702` released a circuit is closed from battery, winding ot sequence switch magnet 1010, upper lett contact of cani 1017, lett hack contact of relay'702 to ground. This circuitadvances sequence switch 1010 to position 16.

Then sequence switch 1010 leaves position 15 the locking circuit of relay 703 is opened as well as the circuit of relay 1033. A circuit is then closed from battery, winding ot sequence switch magnet 910, lower right contact ot cani 920, upper left contact ot cani 1029 to ground, in which circuit sequence switch 910 is advanced to position 17. On reaching position 17 the circuit of relay dL and the locking circuitof relay 9&0 are opened, the release of relay 940 releasing relay 918. WTith relay 918 normal, a circuit is closed troni battery, winding or' magnet 910, upper left contact ot cani 92a, outer right back contact of relay 918 to ground advancing the sequence switch to position 18.l Sequence switch 910 is then advanced to position 1 in a circuit over the lower right contact ot' cani 920, upper lett contact o1C earn 1029 to ground. Relay 701 is held operated over' conductor 729, as long as either sequence switch 1010 or 910 is ott' normal, the circuit extending to ground either at the upper lett contact of cam 1000 or at the lower right contact ot cani 925.

Soquence switch 1010 is advanced lroin po- I sition 16 to position 17 in a circuit over the lower lett contact ot cam 1017, right back contact ot relay 1005 to ground, and from position 17 to position 18 over the upper rightcontact ot cani s, upper Contact ot cani 921 to ground. Then sequence switch 910 has reached position 1. it impulse sequence switch 1210 is also in position 1, a circuit is lclosed for advancing switch 1010 to position 1 over the upper lett contact of cam 10011, conductor 1038, left contacts ot cam 1211,conductor 1212, upper left and lower right contacts ot cam 943 to ground. `With both sequence switches 910 and 1010 in'position 1 relay 701 is released connectj no ing battery through resistance 700 to the.

terminal oli brush 522 indicating that thesender is normal and ready to receive further calls.

rllhe removal or ground `from the left winding` olf relay 519 also causes the release of relay 51S. ltelay 518 in turn releases relay 502 and stop magnet 511. Relay 502 in turn releases relay and relay 505 releases relay 531. rThe release of relay 531 opens the circuit oli stop magnet 521. rlfhe release oi' relay 502 also opens the circuit of relay disconnectino the sender finder 'from the district linder and this circuit is now normal.

When the called subscriber' hangs up his receiver, relay releases in turn release ing relay 207. Relay 238 also opens the holding circuit ot relay 201 andy that relay releases, in turn releasingI relay l/Ylien relay 222 closes its back contact a circuit is conipleted from battery through the wind ing' ot' magnet 210, upper right and lower left Contact oi' cam 211,' lett back Contact of relay 205 lower contacts o1 cam212, back contact of relay 222 to ground. quence switch 210 is advanced to position 18 in this circuit. 1n position 18, the circuit oit downdrive magnet 218 is closed over the lower contacts oit cam 241, let't baci: contact ot relay 205, lower contacts ot cam 2l to ground at the baci; Contact of relay "if The district selector 200 is` restored to normal under the control o1 downdrive niagnet 2134 lilhen the brushes taire up their normal position a circuit is closed from loattcr .through the winding of sequence switch net 210, .lower lett contact oit cani 217, nnniutator segment 2111, brush 28T,lower lett contact ol: cam 219 to ground, restoring the district selector' to normal. Y

viii/viren switch 210 leaves positionfl/z` taround is removed from. brush 255 and the holding,- circuit of relay 801 is oponeth lllhen relay 301 closesitsbacli coirtactit closes a circuit from battery through the winding; oi magnet 310, upper lett Contact ot cam S30-1, outer baci; Contact ot' relay 301 to ground, in which circuit sequence switch :310 is advanced to position 1 8. ln position lil the circuit oit downdrive magnet 322 is closed overV the lower contacts of cam 312 and selector 300 'is restored to normal. ll'heu the brush reaches its normal po` @all 150 o manual office. ln the case ot calls to a manual otiice equipped with-relay call indicator apparatus,theconnection will progress describel tor a mechanical call through oliicefgroup selections except that the class switch will kbe set in position 1,3, 5,101l any odd position.

closes a circuit lfrom battery, winding `of se` qnence swltchmagnet 1210, lower right con-V tact ot' cani 1218, lower right and upper left contacts ot cani 1219, outer right front con tact of relay 12'1L1`to ground. This circuit starts switch 1210 out of position 1 and it is advanced in its rotation to position12 by means of its master cam. reaches position 2 circuit is closed from battery through the windingof relay 1220, lower left and upper right cont-acts of cam 1221, louter right front Contact of relay 1214 to `ground. i Relay 1220 operates and locks overits inner lett front Contact, lower contact oit cam 1216, conductor 1217, upper lett contact of cam 1029 to ground as soon as switch 1210 reaches position 10. This loclringr circuit is closed in positions 10 to 2 of switch 1210.

llhen sequence switch 910 reachespositions 11 and 12 after the completion of otlice group selections a circuit is closed as pre-` viously described for advancing switch 1010 to position 11.- klilith switch 910 in position 12 and sequence switch 1010 in position 11 relay 926 is bridged across the trunk conductors in the manner previously described, except that switch 1200 is set tor relay call indicator operationA and a shunt is closed around resistances 1200 and 1207 lron'i the Contact of cam 1213 over the upper contact olf cam 927. Relay 926 operates in this cir? cuit 4and causes the operation of relays 929 and 930 as before. Relay 930 operates and locks over the lower right contact of `cam 1208, upper. right Contact of cam 931 to ground. As before the operation ot relay 930 closes a shunt around the contacts oi? cam 928, holding relay 926 operated in positions 13 and 14. ltalso closes a circuit from battery, winding' oit' sequence swi'zch magnet 910, lower right Contact of cam 932,"le'tt contact ol" cam 1209.y inner left iront cont-act of relay 930, outer right back contact ol relay 986 to ground, advancing switch 910 to position 13. Sequence switch 1210 at this time has arrived in position 12 and a circuit is completed from battery, winding;v ot magnet 910i When switch 1210 i 

